(1) Field of the Invention
The present invention relates to a capacity control valve for variable control of a capacity or pressure of a working fluid and particularly to a capacity control valve for controlling a discharge amount of a variable capacity compressor or the like used in an air-conditioning system of an automobile or the like according to a pressure load.
(2) Description of Related Art
A swash-plate type variable capacity compressor used in an air-conditioning system of an automobile or the like is provided with a rotating shaft rotated and driven by a rotation force of an engine, a swash plate connected to the rotating shaft with a variable inclination angle, a piston for compression connected to the swash plate and the like, and by varying the inclination angle of the swash plate, a stroke of the piston is changed so as to control the discharge amount of a refrigerant gas.
The inclination angle of the swash plate can be continuously changed by adjusting a pressure balance acting on both faces of the piston through appropriate control of a pressure in a control chamber using a capacity control valve opening/closing-driven by an electromagnetic force while using a suction pressure of a suction chamber suctioning a refrigerant gas, a discharge pressure of a discharge chamber discharging the refrigerant gas pressurized by a piston, and a control chamber pressure of the control chamber (crank chamber) accommodating the swash plate.
As this type of capacity control valve, such a valve is known that is provided with a discharge-side path for having a discharge chamber communicate with a control chamber, a first valve chamber formed in the middle of the discharge-side path, a suction-side path for having a suction chamber communicate with the control chamber, a second valve chamber (operation chamber) formed in the middle of the suction-side path, a valve body formed so that a first valve portion arranged in the first valve chamber for opening/closing the discharge-side path and a second valve portion arranged in the second valve chamber for opening/closing the suction-side path are integrally reciprocated and carry out opening/closing operation in the opposite direction to each other, a third valve chamber (capacity chamber) formed close to the control chamber in the middle of the suction-side path, a pressure sensitive body (bellows) arranged in the third valve chamber, applying an urging force in a direction for extension (expansion) and contracting with increase of the surrounding pressure, a valve seat body (engagement portion) provided at a free end in the expansion/contraction direction of the pressure sensitive body and having a ring-like seat face, a third valve portion (opening-valve connection portion) capable of integrally moving with the valve body in the third valve chamber and opening/closing the suction-side path by engagement/disengagement with/from the valve seat body, a solenoid for applying an electromagnetic driving force to the valve body and the like (See Patent Document 1, for example).
In this capacity control valve, even though a clutch mechanism is not provided at the variable capacity compressor at capacity control, if the control chamber pressure needs to be changed, the pressure in the control chamber (control chamber pressure) can be adjusted by having the discharge chamber communicate with the control chamber. Also, if the control chamber pressure is raised while the variable capacity compressor is stopped, the third valve portion (opening valve connection portion) is disengaged from the valve seat body (engagement portion) so as to open the suction-side path, and the suction chamber is made to communicate with the control chamber.
When the swash plate type variable capacity compressor is stopped, and left for a long time before being started again, a liquid refrigerant (a refrigerant gas cooled during it is left and liquefied) accumulates in the control chamber (crank chamber), and a desired discharge amount can not be ensured by compressing the refrigerant gas unless this liquid refrigerant is discharged.
Thus, in order to provide a desired capacity control immediately after start, this liquid refrigerant should be discharged as rapidly as possible, but in the above conventional capacity control valve, when the suction-side path for having the control chamber communicate with the suction chamber is opened, a relation between the path area formed between the third valve portion (opening valve connection portion) and the valve seat body (engagement portion) and a flow rate is not considered. Therefore, the flow rate of the liquid refrigerant flowing while the third valve portion is opened is small, and a long time is required until the liquid refrigerant is discharged from the control chamber (crank chamber) and secure capacity control can be executed.    Patent Document 1: Unexamined Japanese Patent Publication No. 2003-322086